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Let's assume an averaged sized man (1.8 meters height 80 kg) who's sky-diving from a 5000 m height.

Let's also assume he's using tight clothes and no parachute.

The idea is:

Is it possible for him to survive the fall if he tries to get the maximum velocity he can get by free falling and later, by positioning his body horizontally in a way that resembles a wing shape, get enough upwards impulsion so he can land safely?

EDIT: I was not looking for surviving stories that happened by chance. I was looking for the possibility of a technique that would allow someone (trained) to land safely multiple times, not saying without a scratch but at least without broken bones, and without a special impact area.

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  • $\begingroup$ It might work on a steeply sloped surface. Would you consider that as a special impact area? $\endgroup$ – Alexander Jan 21 '14 at 15:37
  • $\begingroup$ @Alexander Well, the idea was an horizontal surface. So, yes I would consider it a special impact area in this case :) $\endgroup$ – cinico Jan 21 '14 at 15:40
  • $\begingroup$ If you could convert all your downward speed, to forward speed, the road rash would hurt enough to kill you. Maybe a "WingSuit" landing youtube.com/watch?v=Jiy6YvaDmlY $\endgroup$ – Optionparty Jan 21 '14 at 20:13
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So you are asking if the aerodynamic lift can ever exceed the weight and thus slowing the fall. I think the flow around human body is going to stall at the angle of attack needed to get there. Basically the weight to surface area (Wing Load) is too high for controlled flight. This is the reason a wing suit is needed. It increases the surface area, lowering the above ratio and allowing steady flight at an angle of attack which sustains the flow and does not cause a stall condition.

You want the stall speed to be low enough for safe landing, and in our case the stall speed is approxiamtely equal to the free fall speed.

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  • $\begingroup$ Thanks. This is closer to the type of answer I was expecting. But still I think that it requires some background regarding the weight to surface ratio and how it allows you to do a steady flight. It's just because an explanation with "too high" or "too low" "comparing with" seems reasonable but still not enough for a skeptic :) $\endgroup$ – cinico Jan 21 '14 at 15:30
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    $\begingroup$ Look at the performance effects of Wing Loading $\endgroup$ – ja72 Jan 21 '14 at 15:41
  • $\begingroup$ That helps a lot! $\endgroup$ – cinico Jan 21 '14 at 15:44
  • $\begingroup$ I tried to do some math. Considering a man with 80kg with an area of 1.8*0.6, we have a $W_S = 80 kg/m^2$. Density of air 1.2 kg/m^3 and terminal speed of 55 m/s. This gives us the estimation of the $C_L$ coefficient necessary to allow upwards acceleration higher than $g$. Thus, if the man can get a $C_L > 0.44$ he could land safely. $\endgroup$ – cinico Jan 22 '14 at 14:51
  • $\begingroup$ Now you need to add the fact that $C_L$ increases linearly with angle of attack (up to a point) and that $C_D$ increases quadratically with $C_L$. Or $C_D = C_{D_0} + k C_L^2$. $\endgroup$ – ja72 Jan 22 '14 at 14:56
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It already happened that people survive free falls, and is documented. The record, I think, is from a Flight attendant who was sucked out of an airplane in flight...
So, it seems that, under the perfect conditions, if you hit with the perfect angle, and the perfect surface, you just have a slight change to survive; not necessarily be intact, not still have all your limbs... just survive
There is also someone who flew and landed using a wingsuit (no parachute), and managed to land on a runway made of empty cardboard boxes. There's a video of that on youtube. That's not exactly what you asked for but I figured it would interest you anyway.

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    $\begingroup$ Thank you,but I was looking for a different type of answer. The idea was to know if one trained person could not use a parachute and land safely more than once, not only when a miracle happens and without broken bones ;) $\endgroup$ – cinico Jan 21 '14 at 13:07
  • $\begingroup$ In this case, I don't think so... $\endgroup$ – Rolf Jan 21 '14 at 13:08
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    $\begingroup$ @cinico Technically, the wing suit man satisfies your criteria. He didn't use a parachute. He did use a special suit and a giant pile of cardboard boxes. It wasn't from 5000 m, but it was high enough that he was close to terminal velocity anyway. $\endgroup$ – Alan Rominger Jan 21 '14 at 13:28
  • $\begingroup$ @AlanSE Actually, to avoid the cases where a special suit was being used, I tried to specify "tight clothes". $\endgroup$ – cinico Jan 21 '14 at 13:32
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In case you are not aware of it, there is a "lunatic fringe" of free fliers, who are into humans flying without a hang glider. They wear a special suit, that is like a flying fox, generally skin tight, but with a kite wing configuration going from their outstretched arms, along their body, and down the outside of the legs.

They jump out of planes, or base jump, and they achieve a flying or at least gliding speed, and they can fly along the ground, so long as it slopes downward. To terminate, the "flight", they have to gain enough altitude over the ground , so they can pop a chute. They aren't going terminal speed because of the "wings" but very fast anyway; 100 mph region. and the landings are hard. Some have made many such flights honing the art; but the fatal crashes have been significant. It is likely to develop just like base jumping has.

But your concept just won't fly, without some aerodynamic suit.

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Nope the person will attain maximum velocity while striking the ground after he reaches the surface of earth. Thus no matter whatever body shape he makes he is not able to survive as he is not able to displace that amount of air equal to his own weight. Why don't you try thinking when you swim in water you displace the amount of liquid equal to your own weight thus you are able to swim forward backward or in any other direction you want to go. However in case of air you are not able to do so as the intermolecular space between the air particles is large while that for water is less and that for solid is the least thus you are able to walk on any solid surface easily(Neglecting frictional force). So it is absolutely not possible to get your bones intact after hitting the ground with a great velocity. Luckily if any one manage to survive then it is nothing but either a miracle or act of god.

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  • $\begingroup$ But if it was like that, it would also be impossible for an airplane to land. I understand that the impulse will depend on the size and shape of the wing, but I don't see how you are considering it. $\endgroup$ – cinico Jan 21 '14 at 13:41
  • $\begingroup$ The aero plane is able to displace the amount $\endgroup$ – Dws_kool Jan 21 '14 at 14:06
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    $\begingroup$ If you could sustain you statement with some kind of explanation it would be more helpful. As it is, I cannot understand why an airplane can and a person cannot $\endgroup$ – cinico Jan 21 '14 at 14:13
  • $\begingroup$ aeroplane has some engine sort of stuffs that is able to generate energy similar to a fan sort of thing and they are so powerful that they can produce huge amount of energy that is able to make an aero plane able to displace the air equal to its own weight. However it is also possible for a person to displace the air equal to his own weight however for doing that a huge amount of energy is required that may or may not be produced by a person just in case a person is able to generate that much amount of energy to help him fly in the air maybe he can survive the huge fall. $\endgroup$ – Dws_kool Jan 21 '14 at 14:15
  • $\begingroup$ The shape matters a great deal, so this answer is quite misleading. Additionally, there a plenty of planes that fly without engines, so that's not the reason either. $\endgroup$ – Alexander Jan 21 '14 at 15:35

protected by Emilio Pisanty Jan 23 '14 at 11:45

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